.back{
  transform: rotate(180deg);
  position: fixed;
  bottom:120px;
  right:10px;
  font-size: 30px;
  z-index: 10;
}


.fixed{
  position: fixed;
  top: 45px;
  left: 0;
  z-index: 10;
  background: #fff;
  width: 100%;
  margin: 0;
  padding: 10px 0;
  margin-top: 0
}